Any advice on an earth bender monk build would be helpful?

My first thought was way of 4 elements, but it seems to broken, ineffective and burns ki too fast.

Check Tulok's guide on how to build Toph (but take a 12th level of druid insetad of Fighter 1). Basically a combination of Moon Druid and Open Hand Monk with the Wildshapes reflavoured as covering your body in sand and dirt for a "fighting" form. It's a really effective build. 

I made THE BOULDER from AtLA as a character in one of my friend's game. Sadly, it felt to me like there weren't alot of good earth-flavored Elemental Disciplines to use, especially at early levels, so I worked with my DM to homebrew some special options to choose from. He also was nice enough to let me basically have an earth-bending cantrip of sorts (akin to throwing a dart) so it could feel like I was bending more often than not. 

If you listen to forums you’d think that Wizard is the only playable class hahaha

I’ll suggest 4E Monk with the following setup:

1) Elemental Disciplines: Fist of Four Thunders, Gong of the Summit, Fist of Unbroken Air, and if you want to take something like Ride the Wind or Clench of the North Wind, just flavor it so it has some earthen touch.

2) Beyond that, make sure to use Ki-fueled Strike every time you use a Discipline, and maybe grab the Crusher Feat as well to get some additional advantage.  Hold Person will work extremely well in granting you those auto-critical hits, and Crusher will improve your chances as well.

You'll have fun with it I’m sure 🙂 

Also - all Monks burn ki ridiculously fast.  Monks at level 1-5 will constantly be running out of ki, and Monks past level 8 almost struggle to get rid of all their ki (assuming you have a DM that allows you short rests).

Quote from Brewksy >>

 

Also - all Monks burn ki ridiculously fast.  Monks at level 1-5 will constantly be running out of ki, and Monks past level 8 almost struggle to get rid of all their ki (assuming you have a DM that allows you short rests).

Agree and Disagree. I think whats more important here is to manage expectations of using a 4 Elements Monk as a "Bender." If you expect to be like a character from AtLA who almost exclusively bends the elements to fight, then you will burn through all of your ki in a few rounds using your Elemental Disciplines. If thats what you want, then a full caster who has spell slots and elemental cantrips may be more the way to go. Otherwise, if you are okay with your bender actually throwing fists around too, then its just a matter of ki management like you pointed out. 

To add to your suggestions, I would also consider taking Magic Initiate or a similar feat to pick up Mold Earth and a once/long rest casting of something like Earth Tremor or one of the spells from the Elemental Disciplines. Mold Earth (paired with the prestidigitation-esque discipline you get) will give a way to use Earth Bending in roleplay or exploration without drawing on your ki and the extra spell saves you a couple of ki

For the OP. The Four Elements Monk is the least popular subclass for monks and one of the least popular ones in the game as a whole. That is not to say that you can't make a fun and impactful character using that subclass, but many people (myself included) simply find it lacking in a few places compared to other options. If your desire is to play an elemental bender from AtLA universe, then I worry this may not scratch your itch as you will only really get to use your Elemental Disciplines a handful of times across the adventuring day.  

The 4E monk is pretty bad for an Earth bender. Open Hand or reflavoured Astral Self with some druid levels is probably the best and most accurate way to go.

Four Elements isn't just inadequate for this because of burning ki. It's also extremely stingy with disciplines. You get one until 6. Then you have two until 11. The only ones that are natively earth-related are both at level 17.

I'd go with heavy reflavoring to make a bender. I'd do the Boulder as a Barbarian that uses bending to reduce damage when raging. An armorer artificer casting catapult and shield could work too.

If you're willing to look at homebrew content, there are several attempts to make something that works for monks where Four Elements has failed.

Quote from scatterbraind >>

 

If you're willing to look at homebrew content, there are several attempts to make something that works for monks where Four Elements has failed.

 As a shameless plug for my own homebrew, I took two different cracks at reimagining the four elements monk. The first one basically gives mini elemental "smites" and  improvements to Flurry of Blows and Patient Defense (sometimes requiring you to spend an extra ki point). The second one reimagines it as being a sort-of 1/3 caster like the Eldritch Knight or Arcane Trickster. If you DM allows homebrew and either of these interest you, let me know.